1. Field of the Invention
This invention pertains generally to apparatus for the press bending of glass sheets, and more particularly to such apparatus including specially configured conveyor rolls mounted and driven within the confines of a continuous peripheral press bending ring.
2. Description of the Prior Art
In accordance with a widely used procedure for the production of curved or bent glass sheets in large quantities as required in the mass production of glazing units for the automobile industry and the like, sheets are advanced one after another along a generally horizontal path on roll-type conveyors successively through heating and bending areas, and finally through a heat treating area wherein the bent sheets are suitably annealed or tempered, as the case may be, in accordance with the end use for which they are destined.
The glass sheets are heated to their softening point in passing through the heating area, and are then advanced into the bending area and precisely positioned therein between complementary upper and lower shaping members as by engagement of their leading edge by locating stop members projecting into the path of the advancing sheets. The properly oriented sheet is then engaged along its lower marginal of edge portions by the lower press member and lifted from the conveyor rolls to be pressed to the precise predetermined curvature between the complemental shaping surfaces of the press members.
The lower or so called female press member in such press bending apparatus is generally of ring-type construction comprising a peripheral shaping rail which engages only the marginal edges of the sheets in urging them into engagement with the complemental male shaping member. Heretofore, in order to allow the shaping rail of the lower press member to be moved vertically between its lowered and raised positions below and above the conveyor, the shaping rail has been formed of a number of individual segments disposed end-to-end to define the desired outline pattern. The adjacent ends of the segments are spaced apart to provide gaps through which the rolls of the conveyor pass as the shaping rail is raised and lowered. In bending glass sheets of generally rectangular configuration as have been commonly employed in automobiles, the shaping rails are of a substantially rectangular configuration in plan. Thus two sides, generally the long sides, can be formed of continuous segments extending parallel to and positioned between the rolls and the other two sides of the shaping rail, which are oriented normal to the rolls are formed of short segments spaced apart a distance slightly greater than the diameter of the rolls. Since the rolls are of relatively small diameter in the bending section, the spaces or gaps between adjacent segments of the shaping rail can likewise be relatively small so that sagging of the heat-softened glass in the unsupported spaces between adjacent segments will be insignificant, if not non-existent.
As automobile styling has evolved, more complex and elaborate glass shapes of non-rectangular outline have been employed. The similarly configured shaping rails required to bend the glass parts often have portions intersecting the rolls at acute angles. Consequently, the spacing between adjacent shaping rail segments must be increased to the point that difficulty is encountered in press bending the parts to the desired curvatures or shapes due to the tendency of the heat-softened sheets to sag between the widely spaced-apart shaping rail segments. In order to alleviate this problem there has been suggested in U.S. Pat. No. 4,116,662, conveyor rolls formed of two sections individually driven for rotation and rigidly interconnected at their adjacent inner ends so as to require a minimum of clearance openings in the associated press shaping rail to accommodate relative vertical movement between the shaping rail and conveyor rolls. Such rolls nevertheless require that the shaping rail be provided with gaps for accommodating the interconnecting members, as well as mechanism for pivoting the rolls between lowered and raised positions in conjunction with the vertical reciprocating movement of the shaping rails.